Description of the Prior Art
The foregoing products have traditionally been prepared from more expensive sources of hydrocarbons. Dating back to the early part of this century, the large scale production of vinyl chloride, trichloroethylene and perchloroethylene commenced with the use of acetylene. Produces from calcium carbide, which consumes large quantities of electric energy, acetylene remained a relatively expensive raw material. When the ethylene oxychlorination process was developed during the 1950's, acetylene was supplanted by less costly ethylene as a feedstock for chlorinated hydrocarbons. Up to the present time practically all chlorinated ethane/ethylene products have been derived from ethylene.
Although ethylene is produced in large quantities by world-scale plants, its cost is necessarily higher than the price of ethane from which it is preferentially made. Contributing to ethylene's cost is the necessity of employing complex, high-temperature cracking processes with inherent inefficiencies. Therefore, there would be a significant advantage of substituting ethane for ethylene in the manufacture of chlorinated ethane/ethylene provided flexibility is not lost in using any proportion of hydrogen chloride and chlorine as the source of chlorine values. Particularly in the case of the manufacture of vinyl chloride, which requires about 0.45 pounds of ethylene per pound of product, any savings in the cost of hydrocarbon raw material would be important.
In order to circumvent the shortcomings of existing technology, numerous attempts have been made to oxychlorinate ethane by cost-effective means. Methods, for example, employing oxyhalogenation and related technology are described in U.S. Pat. Nos. 3,470,260, 2,334,033, 2,498,546, 3,173,962, 3,345,422, 4,000,205, 4,020,117, 4,284,833, 4,375,569, 4,386,228, 4,446,249, 4,461,919, and 4,467,127.
It is therefore an object of the present invention to provide a method for the chlorination of ethane that overcomes the disadvantages of the conventional methods.
It is also an object to provide a method of the kind described which includes endothermic and exothermic reactions, namely substitution chlorination and dissociation, that are carried out in tandem such that the overall energy requirements can be closely balanced.
These and other objects, features and advantages of the invention will be apparent from the following description and the accompanying drawings in which: